As a conventional and general control method of environmental control devices, an air conditioner is controlled such that the temperature in a room (area) is always kept at a predetermined target temperature. However, there has been also proposed a control method for energy saving such as an intermittent control under which an air conditioner is repeatedly operated and stopped at a certain period of time. Further, Japanese Patent Application Laid-Open No. 2000-205948 discloses a control method in which the presence/absence of persons is recognized by a sensor to activate a device such a television when persons are present and to stop the operation of the device when persons are absent. Japanese Patent Application Laid-Open Publication No. H10-326126 discloses a control method for reducing power consumption in which the presence/absence of persons is recognized by a sensor to activate a personal computer in a normal mode when persons are present and to set a personal computer in an energy saving mode when persons are absent. Further, Japanese Patent Application Laid-Open Publication No. 2006-234243 discloses a control method for performing an environmental control in consideration of comfort and workability in which an area is divided into a plurality of zones, the presence/absence of persons is recognized for each zone, and environmental factors such as a temperature, humidity, and illumination are individually controlled in not only a zone where persons are absent, but also the adjacent zones. Furthermore, Japanese Patent Application Laid-Open Publication No. H05-141743 discloses an environmental control apparatus for controlling equipment in which in accordance with an energy saving level, a comfort level is set low when the energy saving level is high and a comfort level is set high when the energy saving level is low, and the comfort level is calculated using, for example, a PMV calculating method. In addition, Japanese Patent Application Laid-Open Publication No. H10-141735 discloses a method in which some comfortable area patterns are preliminarily stored in a host computer for each of an air-conditioning environment, an illumination environment, and a noise environment based on work types carried out in a space to be environmentally controlled, and the comfortable area patterns are changed for each work type to control the space.